Wind power is one of the fastest growing energy sources around the world. The long-term economic competitiveness of wind power as compared to other energy production technologies is closely related to the reliability and maintenance costs associated with the wind turbine. The wind turbine gearbox is generally the most expensive component to purchase, maintain, and repair.
The conventional vibration monitoring system is based on features uniquely associated with the gearbox bearing design, the gearbox gear design, and the gearbox shaft rotational speeds. For example, in a 1.5 MW wind turbine the speed of a main rotor is amplified approximately two orders of magnitude by a multi-stage gearbox before driving a generator. Thus, the gear and bearing damage signatures are high orders (not necessarily an integral order) of the main shaft rotational frequency. Moreover, in operation, the main shaft speed is not precisely controlled. Therefore, the rotational speed of the main shaft varies based on the wind conditions and the generator loading. A small variation in the main shaft speed may cause significant variations in the bearing and gear vibration feature frequencies, especially the frequencies associated with the high-speed shaft. As a result, the conventional vibration monitoring system may be less effective in providing reliable information under all operating conditions.